Cold flow improver compositions in low-naphthalene solvent naphtha

ABSTRACT

The invention provides a composition comprising A) Solvent Naphtha having a naphthalene content of less than 1% by weight, B) a middle distillate cold flow improver and 
     C) a solubilizing additive selected from aliphatic or alicyclic C 1 - to C 22 -alcohols, cycloaliphatic hydrocarbons and monocyclic aromatic hydrocarbons.

The present invention relates to compositions which comprise a cold flow improver for mineral oils or mineral oil distillates dissolved in low-naphthalene Solvent Naphtha (SN), and a solubilizer.

SN is a product which is obtained in the refining of mineral oils. It is generally a fraction having the following typical properties: Density at 15° C. (to ASTM D1298) 0.86-0.905 g/ml Initial boiling point (to AST > M D1078) 150° C. Final boiling point (to ASTM D1078) 305° C. Saybolt color (to ASTM D156) +25 to +30 Doctor test (to ASTM D235) negative Pensky closed flash test (to ASTM D93) 40° C.-100° C. Aromatics content (HPLC) >90% by weight

SN has hitherto had a high naphthalene content which could be at 10% and more percent by weight. Since naphthalene is suspected of being carcinogenic, the compositions which contain more than 1% by weight of naphthalene are subject to labeling requirements with regard to their possible carcinogenic properties. This has the consequence that SN is prepared with a low naphthalene content.

SN is a customary solvent for middle distillate cold flow improvers. For example, EP-A-0 733 694 discloses middle distillate cold flow improver compositions which, in addition to alcohols and the cold flow improver, also comprise SN.

However, the restriction in the naphthalene content of SN has the consequence that the solvent properties of SN change. For instance, it has been found that the solvent properties of SN having less than 1% by weight of naphthalene are distinctly poorer for middle distillate cold flow improvers than those of SN which is not low in naphthalene.

Since SN is a frequently used solvent for cold flow improvers, the object to be achieved is to find a solubilizer which improves the worsened solvent properties of the low-naphthalene SN for middle distillate cold flow improvers to such an extent that corresponding solutions remain handlable. It is a further object to lower the pour point of these solutions with the solubilizer.

It has been found that, surprisingly, the addition of alcohols and/or certain cyclic hydrocarbons improves the solvent properties of low-naphthalene SN for middle distillate cold flow improvers, and leads to a pour point reduction.

The invention thus provides a composition comprising

-   -   A) Solvent Naphtha having a naphthalene content of less than 1%         by weight,     -   B) a middle distillate cold flow improver and     -   C) a solubilizing additive selected from aliphatic or alicyclic         C₁- to C₂₋₂-alcohols, cycloaliphatic hydrocarbons and monocyclic         aromatic hydrocarbons.

The invention further provides the use of aliphatic or alicyclic C₁- to C₂₂-alcohols, cycloaliphatic hydrocarbons or monocyclic aromatic hydrocarbons as solubilizers and pour point depressants in solutions of Solvent Naphtha having less than 1% by weight naphthalene content and middle distillate cold flow improvers.

The invention further provides a process for preparing solutions of middle distillate cold flow improvers in Solvent Naphtha having less than 1% by weight naphthalene content, by adding to the mixture of these two constituents a solubilizing additive selected from aliphatic or alicyclic C₁- to C₂₂-alcohols, cycloaliphatic hydrocarbons and monocyclic aromatic hydrocarbons.

The invention further provides the use of solutions of middle distillate cold flow improvers in Solvent Naphtha having a naphthalene content of less than 1% by weight, comprising aliphatic or alicyclic C₁- to C₂₂-alcohols, cycloaliphatic hydrocarbons or monocyclic aromatic hydrocarbons as cold additives in middle distillates, biofuel oils or mixtures thereof.

Constituent C) of the inventive composition preferably comprises monohydric alcohols. In a preferred embodiment, the hydrocarbon radicals of the alcohols have from 1 to 12, in particular from 1 to 10, carbon atoms. The hydrocarbon radicals are aliphatic or alicyclic. Examples of suitable alcohols are methanol, ethanol, 2-ethylhexanol and cyclohexanol.

In a further preferred embodiment, constituent C) comprises cycloaliphatic hydrocarbons. These are mono- or polycyclic hydrocarbon radicals which are not aromatic. The cycloaliphatic compounds may be saturated or unsaturated. They comprise preferably from 4 to 18, in particular from 6 to 12, carbon atoms. They may bear substituents, for example amino, carboxyl, keto or aldehyde groups. Examples which can be mentioned here include cyclohexane, norbornane, norbornene and derivatives thereof.

In a further preferred embodiment, constituent C) comprises monocyclic aromatic compounds. These may bear substituents, for example hydroxyl, amino, carboxyl, keto or aldehyde groups. Examples include the isomeric nonylphenols, hydroxybenzenes and salicylaldehyde.

Useful as constituent B) are the customary cold flow improvers for middle distillates.

Examples of such cold flow improvers are polar compounds which bring about paraffin dispersancy (paraffin dispersants), alkylphenol-aldehyde resins, polymeric cold flow improvers and oil-soluble amphiphiles.

For instance, suitable cold flow improvers are those polymers which contain from 10 to 40% by weight of vinyl acetate and from 60 to 90% by weight of ethylene. In a further embodiment of the invention, constituent B) used comprises ethylene/vinyl acetate/vinyl 2-ethylhexanoate terpolymers, ethylene/vinyl acetate/vinyl neononanoate terpolymers and/or ethylene/vinyl acetate/vinyl neodecanoate terpolymers. The terpolymers of vinyl 2-ethylhexanoate, vinyl neononanoate and vinyl neodecanoate contain, apart from ethylene, from 8 to 40% by weight of vinyl acetate and from 1 to 40% by weight of the particular long-chain vinyl esters. In addition to ethylene and from 10 to 40% by weight of vinyl esters and/or from 1 to 40% by weight of long-chain vinyl esters, further preferred copolymers also contain from 0.5 to 20% by weight of olefin having from 3 to 10 carbon atoms, for example isobutylene, diisobutylene, propylene, methylpentene or norbornene.

The paraffin dispersants are preferably low molecular weight or polymeric, oil-soluble compounds having ionic or polar groups, for example amine salts, imides and/or amides. Particularly preferred paraffin dispersants comprise reaction products of secondary fatty amines having from 8 to 36 carbon atoms, in particular dicoconut fatty amine, ditallow fatty amine and distearylamine. Particularly useful paraffin dispersants have been found to be those obtained by reaction of aliphatic or aromatic amines, preferably long-chain aliphatic amines, with aliphatic or aromatic mono-, di-, tri- or tetracarboxylic acids or anhydrides thereof (cf. U.S. Pat. No. 4,211,534). Other paraffin dispersants are copolymers of maleic anhydride and α,β-unsaturated compounds which may optionally be reacted with primary and/or secondary monoalkylamines and/or aliphatic alcohols (cf. EP-A-0 154 177), the reaction products of alkenyl-spiro-bislactones with amines (cf. EP-A-0 413 279 B1) and, according to EP-A-0 606 055 A2, the reaction products of terpolymers based on α,β-unsaturated dicarboxylic anhydrides, α,β-unsaturated compounds and polyoxyalkylene ethers of lower unsaturated alcohols.

Also suitable as constituent B) are esters. These esters derive from polyols having 3 or more OH groups, in particular from glycerol, trimethylolpropane, pentaerythritol, and the oligomers obtainable therefrom by condensation and having from 2 to 10 monomer units, for example polyglycerol. The polyols have generally been reacted with from 1 to 100 mol of alkylene oxide, preferably from 3 to 70 mol, in particular from 5 to 50 mol, of alkylene oxide per mole of polyol. Preferred alkylene oxides are ethylene oxide, propylene oxide and butylene oxide. The alkoxylation is effected by known processes.

The fatty acids suitable for the esterification of the alkoxylated polyols have preferably from 8 to 50, in particular from 12 to 30, especially from 16 to 26, carbon atoms. Suitable fatty acids are, for example, lauric, tridecanoic, myristic, pentadecanoic, palmitic, margaric, stearic, isostearic, arachic and behenic acid, oleic and erucic acid, palmitoleic, myristoleic, ricinoleic acid, and also fatty acid mixtures obtained from natural fats and oils. Preferred fatty acid mixtures contain more than 50% fatty acids having at least 20 carbon atoms. Preferably less than 50% of the fatty acids used for the esterification contain double bonds, in particular less than 10%; they are especially very substantially saturated. Very substantially saturated shall refer here to an iodine number of the fatty acid used of up to 5 g of 1 per 100 g of fatty acid. The esterification may also be effected starting from reactive derivatives of the fatty acids such as esters with lower alcohols (for example methyl or ethyl esters) or anhydrides.

For the esterification of the alkoxylated polyols, it is also possible to use mixtures of the above fatty acids with fat-soluble, polybasic carboxylic acids. Examples of suitable polybasic carboxylic acids are dimer fatty acids, alkenylsuccinic acids and aromatic polycarboxylic acids, and also derivatives thereof such as anhydrides and C₁- to C₅-esters. Preference is given to alkenylsuccinic acids and derivatives thereof with alkyl radicals having from 8 to 200, in particular from 10 to 50 carbon atoms. Examples are dodecenyl-, octadecenyl- and poly(isobutenyl)succinic anhydride. Preference is given to using the polybasic carboxylic acids in minor proportions of up to 30 mol %, preferably from 1 to 20 mol %, in particular from 2 to 10 mol %.

Esters and fatty acids are used for the esterification based on the content of hydroxyl groups on the one hand and carboxyl groups on the other in a ratio of from 1.5:1 to 1:1.5, preferably from 1.1:1 to 1:1.1, in particular in equimolar amounts. The paraffin-dispersing action is particularly marked when an acid excess of up to 20 mol %, especially up to 10 mol %, in particular up to 5 mol %, is used.

The esterification is carried out by customary processes. A particularly useful process has been found to be the reaction of polyol alkoxylate with fatty acid, optionally in the presence of catalysts, for example para-toluenesulfonic acid, C₂- to C₅₀-alkylbenzenesulfonic acids, methanesulfonic acid or acidic ion exchangers. The water of reaction can be removed distillatively by direct condensation or preferably by means of azeotropic distillation in the presence of organic solvents, in particular aromatic solvents such as toluene, xylene or else higher-boiling mixtures such as ®Shellsol A, Shellsol B, Shellsol AB or Solvent Naphtha, or low-naphthalene (<1% by weight) variants of Solvent Naphtha. The esterification is effected preferably fully, i.e. from 1.0 to 1.5 mol of fatty acid per mole of hydroxyl groups are used for the esterification. The acid number of the esters is generally below 15 mg KOH/g, preferably below 10 mg KOH/g, especially below 5 mg KOH/g.

Further preferred paraffin dispersants which are suitable as constituent B) are prepared by reaction of compounds which contain an acyl group with an amine. This amine is a compound of the formula NR⁶R⁷R⁸ where R⁶, R⁷ and R⁸ may be the same or different, and at least one of these groups is C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl, C₈-C₃₆-alkenyl, in particular C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl or cyclohexyl, and the remaining groups are either hydrogen, C₁-C₃₆-alkyl, C₂-C₃₆-alkenyl, cyclohexyl, or a group of the formulae -(A-O)_(x)-E or —(CH₂)_(n)—NYZ, where A is an ethylene or propylene group, x is a number from 1 to 50, E=H, C₁-C₃₀-alkyl, C₅-C₁₂-cycloalkyl or C₆-C₃₀-aryl, and n is 2, 3 or 4, and Y and Z are each independently H, C₁-C₃₀-akyl or -(A-O)_(x). Acyl group refers here to a functional group of the following formula: >C═O

Alkylphenol-aldehyde resins are also suitable as constituent B). Alkylphenol-aldehyde resins are known in principle and are described, for example, in Römpp Chemie Lexikon, 9th edition, Thieme Verlag 1988-92, volume 4, p. 3351ff. The alkyl or alkenyl radicals of the alkylphenol have 6-24, preferably 8-22, in particular 9-18 carbon atoms. They may be linear or preferably branched, in which case the branch may contain secondary and also tertiary structural elements. They are preferably n- and isohexyl, n- and isooctyl, n- and isononyl, n- and isodecyl, n- and isododecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, and also tripropenyl, tetrapropenyl, pentapropenyl and polyisobutenyl up to C₂₄. The alkylphenol-aldehyde resin may also contain up to 20 mol % of phenol units and/or alkylphenols having short alkyl chains, for example butylphenol. For the alkylphenol-aldehyde resin, identical or different alkylphenols may be used.

The aldehyde in the alkylphenol-aldehyde resin has from 1 to 10, preferably from 1 to 4, carbon atoms, and may bear further functional groups. It is preferably an aliphatic aldehyde, more preferably formaldehyde.

The molecular weight of the alkylphenol-aldehyde resins is preferably 350-10 000, in particular 400-5000 g/mol. This corrresponds preferably to a degree of condensation n of from 3 to 40, in particular of from 4 to 20. A prerequisite is that the resins are oil-soluble.

In a preferred embodiment of the invention, these alkylphenol-formaldehyde resins are those which are oligo- or polymers having a repeating structural unit of the formula

where R^(A) is C₆-C₂₄-alkyl or -alkenyl, R^(B) is OH or O—(A-O)_(x)—H where A=C₂-C₄-alkylene and x=from 1 to 50, and n is a number from 2 to 50, in particular from 5 to 40.

The alkylphenol-aldehyde resins are prepared in a known manner by basic catalysis, in which case condensation products of the resol type are formed, or by acidic catalysis, in which case condensation products of the novolak type are formed.

The condensates obtained in both ways are suitable for the inventive compositions. Preference is given to condensation in the presence of acidic catalysts.

To prepare the alkylphenol-aldehyde resins, an alkylphenol having 6-24, preferably 8-22, in particular 9-18, carbon atoms per alkyl group, or mixtures thereof, and at least one aldehyde are reacted with one another, for which about 0.5-2 mol, preferably 0.7-1.3 mol and in particular equimolar amounts of aldehyde are used per mole of alkylphenol compound.

Suitable alkylphenols are in particular n- and isohexylphenol, n- and isooctylphenol, n- and isononylphenol, n- and isodecylphenol, n- and isododecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, tripropenylphenol, tetrapropenylphenol and poly(isobutenyl)phenol up to C₂₄.

The alkylphenols are preferably para-substituted. The alkylphenols may bear one or more alkyl radicals. They are preferably substituted by more than one alkyl group to an extent of at most 5 mol %, in particular to an extent of at most 20 mol % and especially at most 40 mol %. Preferably at most 40 mol %, in particular at most 20 mol %, of the alkylphenols used bear an alkyl radical in the ortho-position. The alkylphenol radicals are especially not substituted by tertiary alkyl groups in the ortho-position to the hydroxyl group.

The aldehyde may be a mono- or dialdehyde and bear further functional groups such as —COOH. Particularly suitable aldehydes are formaldehyde, acetaldehyde, butyraldehyde, glutaraldehyde and glyoxalic acid, preferably formaldehyde. The formaldehyde may be used in the form of paraformaldehyde or in the form of a preferably 20-40% by weight aqueous formalin solution. It is also possible to use corresponding amounts of trioxane.

Finally, in a further embodiment of the invention, comb polymers are used as constituent B). This refers to polymers in which hydrocarbon radicals having at least 8, in particular at least 10, carbon atoms are bonded to a polymer backbone. They are preferably homopolymers whose alkyl side chains contain at least 8 and in particular at least 10 carbon atoms. In copolymers, at least 20%, preferably at least 30%, of the monomers have side chains (cf. Comb-like Polymers-Structure and Properties; N. A. Plate and V. P. Shibaev, J. Polym. Sci. Macromolecular Revs. 1974, 8, 117 ff). Examples of suitable comb polymers are for example, fumarate/vinyl acetate copolymers (cf. EP 0 153 176 A1), copolymers of a C₆-C₂₄-a-olefin and an N—C₆-C₂₂-alkylmaleiimide (cf. EP-A-0 320 766), and also esterified olefin/maleic anhydride copolymers, polymers and copolymers of α-olefins and esterified copolymers of styrene and maleic anhydride.

Comb polymers may be described, for example, by the formula

In this formula,

-   -   A is R′, COOR′, OCOR′, R″-COOR′ or OR′;     -   D is H, CH₃, A or R;     -   E is H or A;     -   G is H, R″, R″-COOR′, an aryl radical or a heterocyclic radical;     -   M is H, COOR″, OCOR″, OR″ or COOH;     -   N is H, R″, COOR″, OCOR, COOH or an aryl radical;     -   R′ is a hydrocarbon chain having 8-150 carbon atoms;     -   R″ is a hydrocarbon chain having from 1 to 10 carbon atoms;     -   m is a number between 0.4 and 1.0; and     -   n is a number between 0 and 0.6.

Constituent A is low-naphthalene SN. It contains preferably less than 1% by weight, in particular at most 0.1% by weight, of naphthalene. The aromatics content of the SN is preferably more than 90% by weight, in particular more than 95% by weight. Its boiling range is preferably between 160 and 230° C.

The inventive composition preferably contains 1-80% by weight of constituent B), from 0.1 to 5% by weight of constituent C) and constituent A) ad 100% by weight.

The composition composed of constituents A), B), and C), and optionally further constituents which are customarily added to middle distillates, contains preferably less than 1% by weight, in particular at most 0.1% by weight, of naphthalene.

In addition to the middle distillate cold flow improvers, the inventive compositions may comprise further constituents which are customarily added to middle distillates. Such constituents are, for example, dewaxing assistants, corrosion inhibitors, antioxidants, lubricity additives, sludge inhibitors, dehazers and additives for lowering the cloud point.

EXAMPLES

Various cold flow improvers specified in Table 1 were dissolved in low-naphthalene and non-low-naphthalene SN, and the pour point (PP) of the solution was determined. TABLE 1 Characterization of the cold flow improvers Viscosity V(140) Degree of branching Designation Type [mPas] CH₃/100 CH₂ A1 MSA-co-C₁₄-α-Olefin (1:1) amidated 5 — with C₁₂ amine A2 MSA-co-C₁₄/₁₆-α-Olefin (1:0.5:0.5) 30 — reacted with C₁₆ amine A3 MSA-co-C₁₆-α-Olefin (1:1) 15 — A4 MSA-co-C₁₂/₁₄-α-Olefin (1:0.5:0.5), 20 — esterified with C₁₈ α-amine A5 13.6 mol % of vinyl acetate 130 3.7 A6 13.7 mol % of vinyl acetate 105 5.3 1.4 mol % of vinyl neodecanoate A7 30 mol % of vinyl neodecanoate 250 2.5 A8 20 mol % of vinyl acetate, 350 8.5 4 mol % of olefin A9 30.5 mol % of vinyl acetate, 170 4.3 7 mol % of vinyl neodecanoate A10  21.3 mol % of vinyl acetate, 105 — 9.2 mol % of vinyl neodecanoate A11  19.5 mol % of vinyl acetate, 90 — 13 mol % of vinyl neodecanoate + A1

TABLE 2 Characterization of the SN qualities Naphthalene Boiling range Aromatics content [° C.] Flashpoint content SN200 6-8%   180-215 61° C. 90% (comparison) A 150 <1% 180-202 >62° C.   97% K 150 ND <1% 180-210 63° C. 99% A 100 <0.1%   164-185 40° C. 99%

Table 3 shows the results of the PP determination which were obtained with the middle distillate cold flow improvers specified in Table 1 in the SN qualities specified in Table 2. TABLE 3 Pour points (PP) without addition of constituent C) Middle distillate PP in PP in PP in PP in cold flow SN200 Visual A150 ND Visual K150 ND Visual A100 Visual improver [° C.] assessment [° C.] assessment [° C.] assessment [° C.] assessment A1 9 clear 27 not free- 18 not free- 12 clear liquid flowing flowing liquid A2 15 clear 24 not free- 24 not free- 15 clear liquid flowing flowing liquid A3 12 clear 21 not free- 27 not free- 9 clear liquid flowing flowing liquid A4 12 clear 24 not free- 21 not free- 12 clear liquid flowing flowing liquid A5 3 clear 9 clear 9 clear 12 clear liquid liquid liquid liquid A6 3 clear 12 clear 9 clear 9 clear liquid liquid liquid liquid A7 42 homoge- 48 not free- 45 not free- 48 not free- neous, flowing flowing flowing opaque A8 27 homoge- 36 not free- 39 not free- 33 not free- neous, flowing flowing flowing opaque A9 9 clear 18 not free- 24 not free- 21 not free- liquid flowing flowing flowing A10  0 clear 15 not free- 15 not free- 12 not free- liquid flowing flowing flowing A11  15 clear 24 not free- 27 not free- 21 not free- liquid flowing flowing flowing

In Table 4, the pour point results obtained with different constituents C) in Solvent Naphtha A150 ND are shown. TABLE 4 Pour point effectiveness of different constituents C) Constituent A was always SN A150 ND Middle distillate Pour point in ° C. with following constituents C cold flow improver none Methanol Cyclohexanol Nonylphenol Salicylaldehyde A1 27 9 12 9 15 A2 24 12 15 12 6 A3 21 9 9 12 12 A4 24 9 15 6 15 A5 9 3 6 3 6 A6 12 6 3 3 6 A7 48 39 42 36 42 A8 36 27 27 24 27 A9 18 9 6 6 9 A10  15 3 0 −3 3 A11  24 15 12 12 15 

1. A composition comprising A) Solvent Naphtha having a naphthalene content of less than 1% by weight, B) a middle distillate cold flow improver and C) a solubilizing additive selected from the group consisting of aliphatic C₁- to C₂₂-alcohols, alicyclic C₁- to C₂₂-alcohols, cycloaliphatic hydrocarbons monocyclic aromatic hydrocarbons, and mixtures thereof.
 2. The composition as claimed in claim 1, wherein constituent C) is a monohydric alcohol.
 3. The composition of claim 1, wherein constituent C) is selected from the group consisting of methanol, ethanol, 2-ethylhexanol, cyclohexanol, and mixtures thereof.
 4. The composition as claimed in claim 1, wherein constituent C) is a mono- or polycyclic hydrocarbon, or mixtures thereof having from 6 to 12 carbon atoms.
 5. The composition as claimed in claim 4, wherein constituent C) is selected from the group consisting of cyclohexane, norbornane, norbornene, and mixtures thereof.
 6. The composition as claimed in claim 1, wherein constituent C) is selected from the group consisting of an isomeric nonylphenol, a hydroxybenzenes, a salicylaldehyde, and mixtures thereof.
 7. The composition of claim 1, wherein constituent B) is a polymer having from 10 to 40% by weight of vinyl acetate and from 60 to 90% by weight of ethylene.
 8. The composition of claim 1, wherein constituent B) is selected from the group consisting of an ethylene/vinyl acetate/vinyl 2-ethylhexanoate terpolymer, ethylene/vinyl acetate/vinyl neononanoate terpolymer, ethylene/vinyl acetate/vinyl neodecanoate terpolymer, and mixtures thereof.
 9. The composition of claim 1, wherein constituent B) is a copolymer which comprises ethylene and from 10 to 40% by weight of vinyl acetate or from 1 to 40% by weight of long-chain vinyl esters, and further comprises from 0.5 to 20% by weight of olefin having from 3 to 10 carbon atoms.
 10. The composition of claim 1, where constituent B is a salt selected from the group consisting of an amine salt, an imide salt, an amide salt, and mixtures thereof, wherein said salt is composed of a secondary fatty amine having from 8 to 36 carbon atoms.
 11. The composition of claim 1, wherein the naphthalene content of constituent A) is at most 0.1% by weight.
 12. The composition of claim 1, where constituent A) has an aromatics content of more than 90% by weight.
 13. A method for improving the cold flow properties of a fuel selected from the group consisting of a middle distillate, a biofuel oil, and mixtures thereof, said method comprising adding to the fuel an additive comprising: a) solvent naphtha having a naphthalene content of less than 1% by weight, and, b) a solubilizing additive selected from the group consisting of a C₁- to C₂₂ aliphatic alcohol, a C₁- to C₂₂ alicyclic alcohol, a cycloaliphatic hydrocarbon, a monocyclic aromatic hydrocarbon, and mixtures thereof.
 14. The composition of claim 9, wherein the long-chain vinyl esters comprise 8 or more carbon atoms per molecule. 